1. Field of the Invention
The present invention relates to a transfer sheet suitable for making ink ribbons for transfer printers, a method of manufacturing the same, and a transfer printing method.
2. Description of the Related Art
FIG. 2 is a typical view of assistance in explaining a conventional transfer sheet and a method of manufacturing the same.
A conventional transfer sheet 20 in the form of an ink ribbon (JP-B No. 6-96307) by way of example comprises a ribbon (base sheet) 21, a plurality of ink regions each of a plurality of color ink regions (yellow, magenta and cyan ink regions), (thermal transfer layers) 22 (22Y, 22M, 22C), and color lines (identification marks) 23 of colors of the color ink regions 22, extending perpendicularly to the length of the ink ribbon.
The transfer sheet 20 is manufactured by a suitable method, such as a gravure printing method, using printing cylinders 201, 202, 203 and 204 each having a circumference three times the length of the ink regions. First, a Y transfer region 22Y is printed by using the yellow (Y) printing cylinder 201, an M transfer region 22M is printed by using the magenta (M) printing cylinder 202, and a C transfer region 22C is printed by using the cyan (C) printing cylinder 203, Finally, the mark printing cylinder 204 prints the identification marks 23.
This method of manufacturing the conventional transfer sheet is not efficient because the transfer layers are printed one by one by using the Y, the M and the C printing cylinder. The efficiency of this method may be improved by using a printing cylinder provided with a plurality of transfer layer printing plates, i.e., multiple plate printing cylinder.
Transfer layers of an ink ribbon printed by using a printing cylinder provided with a plurality of transfer layer printing plates differ subtly in thickness from each other because of dimensional errors in the transfer layer printing plates. When such an ink ribbon is used for printing (transfer printing), colors appear in hues different from expected hues. When a sublimation transfer method capable of full-color image transfer is used, different pictures differ from each other in the gray hue of highlights and middle tone areas.
In general, transfer printers use a plurality of ink ribbons, such as a three-color type of ribbon (Y, M, C), a four-color type of ribbon (Y, M, C, Bk), a ribbon with a protective layer (Y, M, C, OP) or a ribbon with high density.
In a conventional transfer printer, a cassette which contains an ink ribbon, has a detection hole corresponding the ink ribbon for determining the type of the ink ribbon (JP-A No. 64-27981). When the cassette is inserted into the transfer printer, the detection hole is detected by a suitable mechanical measure. Another cassette may have a reflection mark representing the type of a contained ink ribbon, and the reflection mark is detected by a sensor for determining the type of the ink ribbon (JM-A No. 3-29367).
The third method is that a ribbon on which an ink ribbon is wound has a bar-code representing the type of the ink ribbon, and the bar-code is detected by the transfer printer.
However, the above three methods cause the increase of manufacturing costs of printers, because the printers need to be provided with particular mechanisms for detecting the hole, the reflection mark or the bar-code. In addition, the detection hole and the reflection mark should be changed in accordance with the corresponding ink ribbon, which leads cost increase.
Identification marks including information about the type of ink ribbon have been developed to solve the above problems. For example, identification marks representing colors whose number and width are changed in accordance with the type of media for determining the type of media (JP-B No. 6-96307) (JM-B No. 7-12004) (JP-A No. 9-10956).
In this case, however, the area of identification marks and the length of ink ribbon have been increased because of the increase of the number of the identification marks, and therefore the effective recording length and width of the ink ribbon have been shortened.
Accordingly, it is an object of the present invention to provide a transfer sheet capable of being manufactured at a high production efficiency and of forming a transfer-printed image of a satisfactory picture quality, a method of manufacturing the transfer sheet, and a transfer printing method.
According to a first aspect of the present invention, a transfer sheet comprises a base sheet, a thermal transfer layer having a plurality of transfer region sets, each transfer region set having a plurality of transfer regions with functions different from each other, and identification marks formed in the transfer region sets, in which the identification marks formed in the YMC transfer region sets consist of at least two different types.
The identification marks of one transfer region set may be formed by using different printing plates formed on a printing cylinder and may have different forms, respectively.
The identification marks of one transfer region set may be formed in the transfer regions, respectively, the identification marks of the transfer region set may be formed in the same form, and the identification mark formed in one of the transfer regions of the transfer region set may have a characteristic different from those of the identification marks formed in the other transfer regions of the same transfer region set.
The identification marks of one transfer region set may have the same form, and the identification marks of different transfer region sets may have different characteristics, respectively.
According to a second aspect of the present invention, a transfer sheet comprises a base sheet, a thermal transfer layer having a plurality of transfer region sets, each transfer region set having a plurality of transfer regions with functions different from each other, and identification marks formed in the transfer region sets, in which the identification marks comprises an identification mark having a plurality of parts, one part having a characteristic different from those of the other parts.
The identification marks of one transfer region set may be formed in the transfer regions, respectively, and the identification mark formed in one of the transfer regions of the transfer region set may have a characteristic different from those of the identification marks formed in the other transfer regions of the same transfer region set.
According to a third aspect of the present invention, a method of manufacturing a transfer sheet comprising a base sheet, a thermal transfer layer having a plurality of transfer region sets, each transfer region set having a plurality of transfer regions with functions different from each other, and identification marks formed in the transfer region sets comprises the steps of forming the thermal transfer layer having the plurality of transfer region sets on the base sheet by using a plurality of transfer region printing cylinders each provided with a plurality of printing plates for printing the transfer regions of different functions, and forming the different identification marks in the transfer region sets.
The identification marks of one transfer region set may be formed by the different printing plates mounted on the same printing cylinder and may have different forms, respectively.
The identification marks of one transfer region set may be, for each transfer region, formed by the different printing plates mounted on the same printing cylinder in the transfer regions, respectively, the identification marks of the transfer region set may have the same form, and the identification mark of one of the transfer regions of the transfer region set has a characteristic different from those for the identification marks of the other transfer regions of the same transfer region set.
The identification marks of one transfer region set may be formed in the same form by the different printing plates mounted on the same printing cylinder, and the transfer region sets may differ from each other in the characteristics of the identification marks.
A transfer printing method using a transfer sheet comprising a base sheet, a thermal transfer layer having a plurality of transfer region sets, each transfer region set having a plurality of transfer regions with functions different from each other, and identification marks formed in the transfer region sets comprises the steps of recording information in the identification marks of the transfer region sets, reading the identification marks of the transfer region sets, correcting transfer conditions on the basis of the information represented by the identification marks, and transferring the transfer regions.